Lucerne seedling growth and first year productivity in south-eastern Australia as influenced by sowing date in autumn and early winter

Abstract

A field experiment at Tatura, Vic., compared lucerne (Medicago sativa L.) seedling growth and first year productivity of 2 lucerne cultivars (cv. CUF101 and Dekalb 167) sown at monthly intervals from early autumn (March) to early winter (June). At the first hay cut in October, both delayed autumn sowing and the increased winter dormancy between cultivars resulted in significantly lower seedling DM and crop height. Total DM yield from 5 hay cuts during the first cutting season declined as sowing date was delayed. Yields were 18.5, 16.5, 14.5 and 13.1 t ha-1 for the March, April, May and June sowings, respectively. However, no differences in total yield occurred between cultivars despite better early growth of CUF101. During the first 20 weeks from each sowing, significant interactions occurred for seedling DM and crop height between sowing date and cultivar (P=0.05). At 20 weeks of age, seedling DM of the March sown CUF101 was significantly greater than for all other sowings at the same age. At 4 weeks, seedling DM of the June sowings were significantly lower than all others. However, at 20 weeks, seedling DM and crop height of the June sowings were significantly higher than for the April and May sowings. Seedlings of the May sowings remained small for the longest period. The greatest relative differences in seedling DM and crop height occurred at about 10 weeks after sowing where the March sown CUF101 and Dekalb 167 were 29 and 4 1 times greater than the May sown CUF101 and Dekalb 167 respectively. The comparison of seedling DM of the autumn sowings with spring (Sept. and Oct.) sown semi-winter-dormant lucerne (cv. Validor), showed that at 12 weeks of seedling age, seedling DM of the spring sowings was more than double that of the March sown Dekalb 167.